Whirly Corporation's contribution format income statement for the most recent month is shown below:

Required:

$($Consider each case independently$)$:

What would be the revised net operating income per month if the sales volume increases by $60$ units?

What would be the revised net operating income per month if the sales volume decreases by $60$ units?

What would be the revised net operating income per month if the sales volume is $6,400$ units?

Answer is complete but not entirely correct.